1. Field of the Invention
This invention relates to a transparent optical article and a process for preparing the same and more particularly to a transparent optical article constituted of an optical resin and a process for preparing the same.
2. Related Art Statement
Organic polymer materials have hitherto been used as substitutes for inorganic glasses, while taking advantage of their excellent properties that they are transparent and of light weight and they can be handled in safety and easily shaped. Representative examples of organic polymer materials which have been used as organic glasses are polymethyl methacrylate, polydiethyleneglycol bisallyl carbonate, polystyrene and polycarbonate.
These organic polymer materials are used for wide optical applications while taking advantages of the aforementioned merits, although they are inferior to the inorganic glasses in resistance to scratching or abrasion, refractive indices and resistance to heating. However, since the refractive indices of polymethyl methacrylate and polydiethyleneglycol bisallyl carbonate are as low as n.sub.D =1.49 to 1.50, it is inevitable that an optical article designed to have refractive properties, such as a lens, when made of these materials, becomes considerably thicker than that of the article made of an inorganic glass. As a result, these organic polymer materials to not lend themselves to the recent tendency towards reduction in size and weight of the optical materials.
Although polystyrene and polycarbonate have higher refractive indices of n.sub.D =1.59 to 1.60, they are inferior in resistance to solvents and double refraction. In addition, they are generally molded by means of melt molding methods, such as injection molding, while they cannot be easily adapted to cast molding useful for multiitem production system.